scholarly journals Population-based seroprevalence of SARS-CoV-2 and the herd immunity threshold in Maranhão

2020 ◽  
Vol 54 ◽  
pp. 131
Author(s):  
Antônio Augusto Moura da Silva ◽  
Lídio Gonçalves Lima-Neto ◽  
Conceição de Maria Pedrozo e Silva de Azevedo ◽  
Léa Márcia Melo da Costa ◽  
Maylla Luanna Barbosa Martins Bragança ◽  
...  
Keyword(s):  
Herd Immunity ◽  
Household Survey ◽  
Population Based ◽  
Igg Antibodies ◽  
Infection Rates ◽  
Qualitative Detection ◽  
Roche Diagnostics ◽  
Local Herd ◽  
Pharmaceutical Interventions ◽  
Population Based Survey

OBJECTIVE: To estimate the seroprevalence of SARS-CoV-2 in the state of Maranhão, Brazil. METHODS: A population-based household survey was performed, from July 27, 2020 to August 8, 2020. The estimates considered clustering, stratification and non-response. Qualitative detection of IgM and IgG antibodies was performed in a fully-automated Elecsys® Anti-SARS-CoV-2 electrochemiluminescence immunoassay on the Cobas® e601 analyzer (Roche Diagnostics). RESULTS: In total, 3,156 individuals were interviewed. Seroprevalence of total antibodies against SARS-CoV-2 was 40.4% (95%CI 35.6-45.3). Population adherence to non-pharmaceutical interventions was higher at the beginning of the pandemic than in the last month. SARS-CoV-2 infection rates were significantly lower among mask wearers and among those who maintained social and physical distancing in the last month compared to their counterparts. Among the infected, 26.0% were asymptomatic. The infection fatality rate (IFR) was 0.14%, higher for men and older adults. The IFR based on excess deaths was 0.28%. The ratio of estimated infections to reported cases was 22.2. CONCLUSIONS: To the best of our knowledge, the seroprevalence of SARS-CoV-2 estimated in this population-based survey is one of the highest reported. The local herd immunity threshold may have been reached or might be reached soon.

scholarly journals SARS-CoV-2 infection is at herd immunity in the majority segment of the population of Qatar

2021 ◽  
Author(s):  
Mohamed H Al-Thani ◽  
Elmoubasher Farag ◽  
Roberto Bertollini ◽  
Hamad Eid Al Romaihi ◽  
Sami Abdeen ◽  
...  
Keyword(s):  
Total Population ◽  
Herd Immunity ◽  
Geographic Location ◽  
Population Based ◽  
Infection Prevalence ◽  
Cross Sectional ◽  
Previous Infection ◽  
Current Infection ◽  
Polymerase Chain ◽  
Population Based Survey

Abstract Background Qatar experienced a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic that disproportionately affected the craft and manual worker (CMW) population who comprise 60% of the total population. This study aimed to assess ever and/or current infection prevalence in this population. Methods A cross-sectional population-based survey was conducted during July 26-September 09, 2020 to assess both anti-SARS-CoV-2 positivity through serological testing and current infection positivity through polymerase chain reaction (PCR) testing. Associations with antibody and PCR positivity were identified through regression analyses. Results Study included 2,641 participants, 69.3% of whom were <40 years of age. Anti-SARS-CoV-2 positivity was 55.3% (95% CI: 53.3-57.3%) and was significantly associated with nationality, geographic location, educational attainment, occupation, and previous infection diagnosis. PCR positivity was 11.3% (95% CI: 9.9-12.8%) and was significantly associated with nationality, geographic location, occupation, contact with an infected person, and reporting two or more symptoms. Infection positivity (antibody and/or PCR positive) was 60.6% (95% CI: 58.6-62.5%). The proportion of antibody-positive CMWs that had a prior SARS-CoV-2 diagnosis was 9.3% (95% CI: 7.9-11.0%). Only seven infections were ever severe and one was ever critical—an infection severity rate of 0.5% (95% CI: 0.2-1.0%). Conclusions Six in every 10 CMWs have been infected, suggestive of reaching the herd immunity threshold. Infection severity was low with only one in every 200 infections progressing to be severe or critical. Only one in every 10 infections had been previously diagnosed suggestive of mostly asymptomatic or mild infections.

scholarly journals Seroprevalence of SARS-CoV-2 infection in the craft and manual worker population of Qatar

2020 ◽  
Author(s):  
Mohamed H. Al-Thani ◽  
Elmoubasher Farag ◽  
Roberto Bertollini ◽  
Hamad Eid Al Romaihi ◽  
Sami Abdeen ◽  
...  
Keyword(s):  
Total Population ◽  
Herd Immunity ◽  
Geographic Location ◽  
Population Based ◽  
Cross Sectional ◽  
Manual Worker ◽  
Previous Infection ◽  
Current Infection ◽  
Polymerase Chain ◽  
Population Based Survey

ABSTRACTBackgroundQatar experienced a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic that disproportionately affected the craft and manual worker (CMW) population who comprise 60% of the total population. This study aimed to assess the proportions of ever and/or current infection in this population.MethodsA cross-sectional population-based survey was conducted during July 26-September 09, 2020 to assess both anti-SARS-CoV-2 positivity through serological testing and polymerase chain reaction (PCR) positivity through PCR testing. Associations with antibody and PCR positivity were identified through regression analyses.ResultsStudy included 2,641 participants, 69.3% of whom were <40 years of age. Anti-SARS-CoV-2 positivity was estimated at 55.3% (95% CI: 53.3-57.3%) and was significantly associated with nationality, geographic location, educational attainment, occupation, presence of symptoms in the two weeks preceding the survey, and previous infection diagnosis. PCR positivity was assessed at 11.3% (95% CI: 9.9-12.8%) and was significantly associated with geographic location, contact with an infected person, and reporting two or more symptoms. Infection positivity (antibody and/or PCR positive) was assessed at 60.6% (95% CI: 9.9-12.8%). The proportion of antibody-positive CMWs that had a prior SARS-CoV-2 diagnosis was 9.3% (95% CI: 7.9-11.0%). Only seven infections were ever severe and one was ever critical—an infection severity rate of 0.5% (95% CI: 0.2-1.0%).ConclusionsSix in every 10 CMWs have been infected, suggestive of reaching the herd immunity threshold. Infection severity was low with only one in every 200 infections progressing to be severe or critical. Only one in every 10 infections had been previously diagnosed suggestive of mostly asymptomatic or minimally mild infections.

scholarly journals The Prevalence of Acute and Chronic Malnutrition Among Children Under Five in a Rural Haitian Town: A Population-Based Survey (P11-103-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Connor Orrico ◽  
Jon Zelasko ◽  
Vinny Polsinelli ◽  
Vijay Aswani
Keyword(s):  
Household Survey ◽  
Population Based ◽  
Western Hemisphere ◽  
Acute Malnutrition ◽  
Formal Schooling ◽  
Middle Income ◽  
Persistent Problem ◽  
Malnourished Children ◽  
Low Middle Income Countries ◽  
Population Based Survey

Abstract Objectives Both chronic and acute malnutrition in children under 5 remain a persistent problem in low and low-middle income countries. Haiti faces the highest burden of childhood malnutrition in the Western Hemisphere. We attempted to describe the prevalence of malnutrition in children in a farming community in Haiti and record characteristics of the those experiencing the disease. Methods A household survey was conducted within the town of Fontaine in the Nord department of Haiti on all children under the age of 5. A total of 535 children were assessed. Anthropometric data was taken on the children and household information was assessed via a population-based survey. Results Of the children assessed, 28% (149/535) were either chronically or acutely malnourished. Of the children who were malnourished: 36.4% (43/118) had 3 or more bouts of diarrhea in the past 3 months and only 5.3% (7/132) had stopped breastfeeding before 1 year of age. On average, the mothers of these children had completed 6.2 years of formal schooling. A slight majority of mothers, 54.7% (81/148), either “never” or “rarely” were concerned their child was malnourished. Of the households with malnourished children 88.4% (130/147) had reported running out of food in the last month. When asked what caused children in Fontaine to be malnourished, mothers of malnourished children cited a lack of food, 56.2% (82/146), and a lack of access to employment, 25.3% (37/146), most frequently. Conclusions Malnutrition commonly affects children in Fontaine. Efficacious prevention interventions could possibly include decreasing food insecurity, or increasing girls’ education level. Funding Sources None.

scholarly journals Population-based seroprevalence of SARS-CoV-2 is more than halfway through the herd immunity threshold in the State of Maranhao, Brazil

2020 ◽  
Author(s):  
Antônio Augusto Moura da Silva ◽  
Lídio Gonçalves Lima Neto ◽  
Conceição de Maria Pedrozo e Silva Azevedo ◽  
Léa Márcia Melo da Costa ◽  
Maylla Luana Barbosa Martins Bragança ◽  
...  
Keyword(s):  
False Negative ◽  
Herd Immunity ◽  
Age Groups ◽  
Household Survey ◽  
Population Based ◽  
The State ◽  
Cluster Sampling ◽  
Fatality Rate ◽  
Negative Results ◽  
Electrochemiluminescence Immunoassay

Background: Few population-based studies on the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been performed to date, and most of them have used lateral flow immunoassays with finger-prick, which may yield false-negative results and thus underestimate the true infection rate. Methods: A population-based household survey was performed in the State of Maranhao, Brazil, from 27 July 2020 to 8 August 2020 to estimate the seroprevalence of SARS-CoV-2 using a serum testing electrochemiluminescence immunoassay. A three-stage cluster sampling stratified by four state regions was used. The estimates took clustering, stratification, and non-response into account. Qualitative detection of IgM and IgG antibodies was performed in a fully-automated Elecsys Anti-SARS-CoV-2 electrochemiluminescence immunoassay on the Cobas e601 analyser (Roche Diagnostics). Findings: A total of 3156 individuals were interviewed. Seroprevalence of total antibodies against SARS-CoV-2 was 40.4% (95%CI 35.6-45.3). Population adherence to non-pharmaceutical interventions was higher at the beginning of the pandemic than in the last month. SARS-CoV-2 infection rates were significantly lower among mask wearers and among those who maintained social and physical distancing in the last month compared to their counterparts. Among the infected, 62.2% had more than three symptoms, 11.1% had one or two symptoms, and 26.0% were asymptomatic. The infection fatality rate was 0.17%, higher for males and advanced age groups. The ratio of estimated infections to reported cases was 22.2. Interpretation: To the best of our knowledge, the seroprevalence of SARS-CoV-2 estimated in this population-based survey was the highest and the closest to the herd immunity threshold reported to date. Our results suggest that the herd immunity threshold is not as low as 20%, but at least higher than or equal to around 40%. The infection fatality rate was one of the lowest reported so far, and the proportion of asymptomatic cases was low.

scholarly journals Repeated seroprevalence of anti-SARS-CoV-2 IgG antibodies in a population-based sample

2020 ◽  
Author(s):  
Silvia Stringhini ◽  
Ania Wisniak ◽  
Giovanni Piumatti ◽  
Andrew S. Azman ◽  
Stephen A. Lauer ◽  
...  
Keyword(s):  
Test Performance ◽  
Wide Spectrum ◽  
Herd Immunity ◽  
Population Based ◽  
Bayesian Regression ◽  
Enzyme Linked Immunosorbent Assay ◽  
Igg Antibodies ◽  
Case Definitions ◽  
Adult Participants ◽  
Household Members

AbstractBackgroundAssessing the burden of COVID-19 based on medically-attended case counts is suboptimal given its reliance on testing strategy, changing case definitions and the wide spectrum of disease presentation. Population-based serosurveys provide one avenue for estimating infection rates and monitoring the progression of the epidemic, overcoming many of these limitations.MethodsTaking advantage of a pool of adult participants from population-representative surveys conducted in Geneva, Switzerland, we implemented a study consisting of 8 weekly serosurveys among these participants and their household members older than 5 years. We tested each participant for anti-SARS-CoV-2-IgG antibodies using a commercially available enzyme-linked immunosorbent assay (Euroimmun AG, Lübeck, Germany). We estimated seroprevalence using a Bayesian regression model taking into account test performance and adjusting for the age and sex of Geneva’s population.ResultsIn the first three weeks, we enrolled 1335 participants coming from 633 households, with 16% <20 years of age and 53.6% female, a distribution similar to that of Geneva. In the first week, we estimated a seroprevalence of 3.1% (95% CI 0.2-5.99, n=343). This increased to 6.1% (95% CI 2.69.33, n=416) in the second, and to 9.7% (95% CI 6.1-13.11, n=576) in the third week. We found that 5-19 year-olds (6.0%, 95% CI 2.3-10.2%) had similar seroprevalence to 20-49 year olds (8.5%, 95%CI 4.99-11.7), while significantly lower seroprevalence was observed among those 50 and older (3.7%, 95% CI 0.99-6.0, p=0.0008).InterpretationAssuming that the presence of IgG antibodies is at least in the short-term associated with immunity, these results highlight that the epidemic is far from burning out simply due to herd immunity. Further, no differences in seroprevalence between children and middle age adults are observed. These results must be considered as Switzerland and the world look towards easing restrictions aimed at curbing transmission.

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